The present invention relates to a microwave oven capable of automatically changing its microwave output power in accordance with desired time schedule selected for the kind and amount of the cooking, so that delicate cooking such as stewing can be made easily and safely without boiling over or scorching.
Microwave ovens with provisions for changing microwave power output between two or more levels are known. In such known microwave ovens, the changing of power output is effected by switching capacitors in a voltagedoubler rectifier circuit for supplying the power to the magnetron or by intermittently switching the microwave oscillator on and off at a preset alternating rate by means of thyristors or other semiconductor switches. However, such microwave ovens are not optimum for cooking stews and soups or the like where relatively long periods of simmering at a constant temperature are required.
For stewing, it is desirable first apply an intensive heating for a short time period, for instance, 20 minutes, and then simmer for a longer time period keeping the cooked matter at around 90.degree. C. In the conventional microwave oven, it is necessary manually to switch the circuit so as to lower the microwave output, and then again manually to switch the circuit off after the long time period, for instance 2 hours.